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Full Discussion: How to improve grep performance...
Top Forums Shell Programming and Scripting How to improve grep performance... Post 302166956 by otheus on Wednesday 13th of February 2008 06:19:35 AM
Old 02-13-2008
Quote:
Originally Posted by pooga17

Code:
grep abc file | sort -u | awk '{print #3}' > out_file

I think you mean $3, not #3.

Quote:
Then i am searching content of out_file in muliple files... by using below mentioned command..

grep -f out_file l*view_data_file
What's with the |* ? Is that a typo?

Do you need to know which file contains the string? If not, it would be faster to merge all the files together, and then do the grep.

Code:
cat *data_files.dat  | grep -f out_file

Otherwise, you can do a parallelized search, assuming you can take advantage of a multi-CPU system:
Code:
for f in *data_files.dat ; do
   grep -f out_file $f  >>grep-out.$$  & 
done
wait
cat grep-out.$$

Of course, if there are thousands of dat files, this might bring the system "to its knees". In that case, you can have each grep do 5 at a time.

Code:
ls -1 *data_files.dat | 
while read f1; do
  read f2
  read f3
  read f4
  read f5
  grep -f out_file $f1 $f2 $f3 $f4 $f5 >>grep-out.$$ &
done

If any files contain spaces or strange characters, you'll need to enclose each variable in double-quotes.
 

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LEARN ABOUT NETBSD

zfgrep

ZGREP(1)						    BSD General Commands Manual 						  ZGREP(1)

NAME

     zgrep, zegrep, zfgrep -- print lines matching a pattern in gzip-compressed files

SYNOPSIS

     zgrep [grep-flags] [--] pattern [files ...]

     zegrep [grep-flags] [--] pattern [file ...]

     zfgrep [grep-flags] [--] pattern [file ...]

DESCRIPTION

     zgrep runs grep(1) on files or stdin, if no files argument is given, after decompressing them with zcat(1).

     The grep-flags and pattern arguments are passed on to grep(1).  If an -e flag is found in the grep-flags, zgrep will not look for a pattern
     argument.

     zegrep calls egrep(1), while zfgrep calls fgrep(1).

EXIT STATUS

     In case of missing arguments or missing pattern, 1 will be returned, otherwise 0.

SEE ALSO

     egrep(1), fgrep(1), grep(1), gzip(1), zcat(1)

AUTHORS

     Thomas Klausner <wiz@NetBSD.org>

BSD
								 December 28, 2003							       BSD
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